One aspect of the present invention relates to a pipe fitting for connecting between dissimilar pipes, or the like, and, more particularly, for connecting between metallic and polymeric pipes, or the like. Another aspect of the present invention relates to such a pipe fitting made substantially, preferably entirely, of polymeric materials. A further aspect of the invention relates to a pipe fitting of the described type wherein differing portions or parts of the fitting are made compositely of different polymeric materials.
It is common for substances to flow between metallic and polymeric pipes that are connected by a pipe fitting, sometimes commonly referred to as a transition fitting. As a more specific example, water is often supplied from an upstream metallic pipe to a downstream polymeric pipe that is the inlet of a plumbing fixture or appliance, such as a faucet or the like. It is critical for this type of pipe fitting to remain watertight, often for very many years. Nonetheless, it is common for some of these pipe fittings to occasionally fail, since they are typically exposed to many cycles of stress caused by variations in the pressure and/or temperature of the water being supplied.
A known pipe fitting for connecting between metallic and polymeric pipes is formed by separately manufacturing generally cylindrical polymeric and metallic bodies, and then connecting the bodies to one another. The polymeric body is inserted into an annular opening of the metallic body, and then the annular edge of the opening is bent inward (e.g., crimped) to hold the polymeric body in the metallic body. For this known pipe fitting, the polymeric body extends around a passageway of the pipe fitting and defines a first opening to the passageway, and the first opening is for being mated to the polymeric pipe. In addition, the metallic body extends around the polymeric body and defines a second opening to the passageway, and the second opening is for being mated to the metallic pipe. These pipe fittings have been known to fail at the crimp, because the crimping can weaken the metallic body.
An environmental disadvantage of known fittings which are formed compositely of both metal and plastic materials is that the brass alloys commonly used in many such fittings contain lead which may leach out of the fitting into water flowing through the fitting. Also, such composite fittings suffer failures in use due to “dezincification” by gradual extraction of the zinc content in brass alloys causing the brass to become porous and brittle.
Accordingly, there is a need in the industry for improved pipe fittings for connecting between metallic and polymeric pipes.